│ Implement a class for a stack that supports all the regular │functions │ (push, pop) and an additional function of max() which returns │the │ maximum element in the stack (return None if the stack is │empty). Each │ method should run in constant time. │class MaxStack: │ def init(self): │ # Fill this in. │ def push(self, val): │ # Fill this in. │ def pop(self): │ # Fill this in. │ def max(self): │ # Fill this in. │s = MaxStack() │s.push(1) │s.push(2) │s.push(3) │s.push(2) │print s.max() │# 3 │s.pop() │s.pop() │print s.max() │# 2